24 July 2021 Precision Alloys
4j33 Precision Alloy Steel Bar
4J33 (Kovar) is a kind of precision alloy with abnormal thermal expansion characteristics, also known as thermal expansion alloy, widely used in the electronics industry, precision measuring tools, precision instruments and low-temperature engineering and other fields.
The general expansion of the metal and alloy when heated, the amount of expansion increases linearly with increasing temperature, but some of the alloy thermal expansion curve at a certain temperature bending point (different slope of the two lines of tangent intersection, as shown in the figure Tk) , The coefficient of thermal expansion below the bend point is much lower than the normal thermal expansion coefficient above the bend point, which is called the anomalous thermal expansion characteristic.
Expansion alloy is divided into low expansion alloy and fixed expansion alloy, which is also known as sealing alloy. The average expansion coefficient of the low expansion alloy below the bending point is less than 3 × 10-6 ℃ -1; the average expansion coefficient of the fixed expansion alloy below the bending point is about (4 ~ 10) × 10-6 ℃ -1. The Fe-Ni, Fe-Ni-Co, and Fe-Ni-Cr alloys are mainly composed of high-chrome and Co-Fe-Cr alloys.
They are also used as expansion alloys. Expansion alloy in addition to a specific coefficient of thermal expansion, according to different uses also requires good sealing, weldability, corrosion resistance, machinability and machinability, and in the use of temperature range is not allowed to cause expansion characteristics Significantly changed phase change. Expansion alloy in the manufacturing process must accurately control the chemical composition of the alloy, its products are generally barred, sheet, strip, wire, and pipe.